/*
 * Copyright (c) 2007, 2021, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xpath.internal;

import javax.xml.transform.ErrorListener;
import javax.xml.transform.TransformerException;

import com.sun.org.apache.xalan.internal.res.XSLMessages;
import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xml.internal.dtm.DTMIterator;
import com.sun.org.apache.xml.internal.utils.XMLString;
import com.sun.org.apache.xpath.internal.objects.XNodeSet;
import com.sun.org.apache.xpath.internal.objects.XObject;
import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;

import org.xml.sax.ContentHandler;

/**
 * This abstract class serves as the base for all expression objects.  An
 * Expression can be executed to return a {@link com.sun.org.apache.xpath.internal.objects.XObject},
 * normally has a location within a document or DOM, can send error and warning
 * events, and normally do not hold state and are meant to be immutable once
 * construction has completed.  An exception to the immutibility rule is iterators
 * and walkers, which must be cloned in order to be used -- the original must
 * still be immutable.
 */
public abstract class Expression implements java.io.Serializable, ExpressionNode, XPathVisitable {
    static final long serialVersionUID = 565665869777906902L;
    /**
     * The location where this expression was built from.  Need for diagnostic
     * messages. May be null.
     *
     * @serial
     */
    private ExpressionNode m_parent;

    /**
     * Tell if this expression or it's subexpressions can traverse outside
     * the current subtree.
     *
     * @return true if traversal outside the context node's subtree can occur.
     */
    public boolean canTraverseOutsideSubtree() {
        return false;
    }

//  /**
//   * Set the location where this expression was built from.
//   *
//   *
//   * @param locator the location where this expression was built from, may be
//   *                null.
//   */
//  public void setSourceLocator(SourceLocator locator)
//  {
//    m_slocator = locator;
//  }

    /**
     * Execute an expression in the XPath runtime context, and return the
     * result of the expression.
     *
     * @param xctxt       The XPath runtime context.
     * @param currentNode The currentNode.
     * @return The result of the expression in the form of a <code>XObject</code>.
     * @throws javax.xml.transform.TransformerException if a runtime exception
     *                                                  occurs.
     */
    public XObject execute(XPathContext xctxt, int currentNode)
            throws javax.xml.transform.TransformerException {

        // For now, the current node is already pushed.
        return execute(xctxt);
    }

    /**
     * Execute an expression in the XPath runtime context, and return the
     * result of the expression.
     *
     * @param xctxt       The XPath runtime context.
     * @param currentNode The currentNode.
     * @param dtm         The DTM of the current node.
     * @param expType     The expanded type ID of the current node.
     * @return The result of the expression in the form of a <code>XObject</code>.
     * @throws javax.xml.transform.TransformerException if a runtime exception
     *                                                  occurs.
     */
    public XObject execute(
            XPathContext xctxt, int currentNode, DTM dtm, int expType)
            throws javax.xml.transform.TransformerException {

        // For now, the current node is already pushed.
        return execute(xctxt);
    }

    /**
     * Execute an expression in the XPath runtime context, and return the
     * result of the expression.
     *
     * @param xctxt The XPath runtime context.
     * @return The result of the expression in the form of a <code>XObject</code>.
     * @throws javax.xml.transform.TransformerException if a runtime exception
     *                                                  occurs.
     */
    public abstract XObject execute(XPathContext xctxt)
            throws javax.xml.transform.TransformerException;

    /**
     * Execute an expression in the XPath runtime context, and return the
     * result of the expression, but tell that a "safe" object doesn't have
     * to be returned.  The default implementation just calls execute(xctxt).
     *
     * @param xctxt         The XPath runtime context.
     * @param destructiveOK true if a "safe" object doesn't need to be returned.
     * @return The result of the expression in the form of a <code>XObject</code>.
     * @throws javax.xml.transform.TransformerException if a runtime exception
     *                                                  occurs.
     */
    public XObject execute(XPathContext xctxt, boolean destructiveOK)
            throws javax.xml.transform.TransformerException {
        return execute(xctxt);
    }


    /**
     * Evaluate expression to a number.
     *
     * @param xctxt The XPath runtime context.
     * @return The expression evaluated as a double.
     * @throws javax.xml.transform.TransformerException
     */
    public double num(XPathContext xctxt)
            throws javax.xml.transform.TransformerException {
        return execute(xctxt).num();
    }

    /**
     * Evaluate expression to a boolean.
     *
     * @param xctxt The XPath runtime context.
     * @return false
     * @throws javax.xml.transform.TransformerException
     */
    public boolean bool(XPathContext xctxt)
            throws javax.xml.transform.TransformerException {
        return execute(xctxt).bool();
    }

    /**
     * Cast result object to a string.
     *
     * @param xctxt The XPath runtime context.
     * @return The string this wraps or the empty string if null
     * @throws javax.xml.transform.TransformerException
     */
    public XMLString xstr(XPathContext xctxt)
            throws javax.xml.transform.TransformerException {
        return execute(xctxt).xstr();
    }

    /**
     * Tell if the expression is a nodeset expression.  In other words, tell
     * if you can execute {@link #asNode(XPathContext) asNode} without an exception.
     *
     * @return true if the expression can be represented as a nodeset.
     */
    public boolean isNodesetExpr() {
        return false;
    }

    /**
     * Return the first node out of the nodeset, if this expression is
     * a nodeset expression.
     *
     * @param xctxt The XPath runtime context.
     * @return the first node out of the nodeset, or DTM.NULL.
     * @throws javax.xml.transform.TransformerException
     */
    public int asNode(XPathContext xctxt)
            throws javax.xml.transform.TransformerException {
        DTMIterator iter = execute(xctxt).iter();
        return iter.nextNode();
    }

    /**
     * Given an select expression and a context, evaluate the XPath
     * and return the resulting iterator.
     *
     * @param xctxt       The execution context.
     * @param contextNode The node that "." expresses.
     * @return A valid DTMIterator.
     * @throws TransformerException                     thrown if the active ProblemListener decides
     *                                                  the error condition is severe enough to halt processing.
     * @throws javax.xml.transform.TransformerException
     * @xsl.usage experimental
     */
    public DTMIterator asIterator(XPathContext xctxt, int contextNode)
            throws javax.xml.transform.TransformerException {

        try {
            xctxt.pushCurrentNodeAndExpression(contextNode, contextNode);

            return execute(xctxt).iter();
        } finally {
            xctxt.popCurrentNodeAndExpression();
        }
    }

    /**
     * Given an select expression and a context, evaluate the XPath
     * and return the resulting iterator, but do not clone.
     *
     * @param xctxt       The execution context.
     * @param contextNode The node that "." expresses.
     * @return A valid DTMIterator.
     * @throws TransformerException                     thrown if the active ProblemListener decides
     *                                                  the error condition is severe enough to halt processing.
     * @throws javax.xml.transform.TransformerException
     * @xsl.usage experimental
     */
    public DTMIterator asIteratorRaw(XPathContext xctxt, int contextNode)
            throws javax.xml.transform.TransformerException {

        try {
            xctxt.pushCurrentNodeAndExpression(contextNode, contextNode);

            XNodeSet nodeset = (XNodeSet) execute(xctxt);
            return nodeset.iterRaw();
        } finally {
            xctxt.popCurrentNodeAndExpression();
        }
    }


    /**
     * Execute an expression in the XPath runtime context, and return the
     * result of the expression.
     *
     * @param xctxt The XPath runtime context.
     *              NEEDSDOC @param handler
     * @return The result of the expression in the form of a <code>XObject</code>.
     * @throws javax.xml.transform.TransformerException if a runtime exception
     *                                                  occurs.
     * @throws org.xml.sax.SAXException
     */
    public void executeCharsToContentHandler(
            XPathContext xctxt, ContentHandler handler)
            throws javax.xml.transform.TransformerException,
            org.xml.sax.SAXException {

        XObject obj = execute(xctxt);

        obj.dispatchCharactersEvents(handler);
        obj.detach();
    }

    /**
     * Tell if this expression returns a stable number that will not change during
     * iterations within the expression.  This is used to determine if a proximity
     * position predicate can indicate that no more searching has to occur.
     *
     * @return true if the expression represents a stable number.
     */
    public boolean isStableNumber() {
        return false;
    }

    /**
     * This function is used to fixup variables from QNames to stack frame
     * indexes at stylesheet build time.
     *
     * @param vars List of QNames that correspond to variables.  This list
     *             should be searched backwards for the first qualified name that
     *             corresponds to the variable reference qname.  The position of the
     *             QName in the vector from the start of the vector will be its position
     *             in the stack frame (but variables above the globalsTop value will need
     *             to be offset to the current stack frame).
     *             NEEDSDOC @param globalsSize
     */
    public abstract void fixupVariables(java.util.Vector vars, int globalsSize);

    /**
     * Compare this object with another object and see
     * if they are equal, include the sub heararchy.
     *
     * @param expr Another expression object.
     * @return true if this objects class and the expr
     * object's class are the same, and the data contained
     * within both objects are considered equal.
     */
    public abstract boolean deepEquals(Expression expr);

    /**
     * This is a utility method to tell if the passed in
     * class is the same class as this.  It is to be used by
     * the deepEquals method.  I'm bottlenecking it here
     * because I'm not totally confident that comparing the
     * class objects is the best way to do this.
     *
     * @return true of the passed in class is the exact same
     * class as this class.
     */
    protected final boolean isSameClass(Expression expr) {
        if (null == expr)
            return false;

        return (getClass() == expr.getClass());
    }

    /**
     * Warn the user of an problem.
     *
     * @param xctxt The XPath runtime context.
     * @param msg   An error msgkey that corresponds to one of the conststants found
     *              in {@link com.sun.org.apache.xpath.internal.res.XPATHErrorResources}, which is
     *              a key for a format string.
     * @param args  An array of arguments represented in the format string, which
     *              may be null.
     * @throws TransformerException                     if the current ErrorListoner determines to
     *                                                  throw an exception.
     * @throws javax.xml.transform.TransformerException
     */
    public void warn(XPathContext xctxt, String msg, Object[] args)
            throws javax.xml.transform.TransformerException {

        java.lang.String fmsg = XSLMessages.createXPATHWarning(msg, args);

        if (null != xctxt) {
            ErrorListener eh = xctxt.getErrorListener();

            // TO DO: Need to get stylesheet Locator from here.
            eh.warning(new TransformerException(fmsg, xctxt.getSAXLocator()));
        }
    }

    /**
     * Tell the user of an assertion error, and probably throw an
     * exception.
     *
     * @param b   If false, a runtime exception will be thrown.
     * @param msg The assertion message, which should be informative.
     * @throws RuntimeException                         if the b argument is false.
     * @throws javax.xml.transform.TransformerException
     */
    public void assertion(boolean b, java.lang.String msg) {

        if (!b) {
            java.lang.String fMsg = XSLMessages.createXPATHMessage(
                    XPATHErrorResources.ER_INCORRECT_PROGRAMMER_ASSERTION,
                    new Object[]{msg});

            throw new RuntimeException(fMsg);
        }
    }

    /**
     * Tell the user of an error, and probably throw an
     * exception.
     *
     * @param xctxt The XPath runtime context.
     * @param msg   An error msgkey that corresponds to one of the constants found
     *              in {@link com.sun.org.apache.xpath.internal.res.XPATHErrorResources}, which is
     *              a key for a format string.
     * @param args  An array of arguments represented in the format string, which
     *              may be null.
     * @throws TransformerException                     if the current ErrorListoner determines to
     *                                                  throw an exception.
     * @throws javax.xml.transform.TransformerException
     */
    public void error(XPathContext xctxt, String msg, Object[] args)
            throws javax.xml.transform.TransformerException {

        java.lang.String fmsg = XSLMessages.createXPATHMessage(msg, args);

        if (null != xctxt) {
            ErrorListener eh = xctxt.getErrorListener();
            TransformerException te = new TransformerException(fmsg, this);

            eh.fatalError(te);
        }
    }

    /**
     * Get the first non-Expression parent of this node.
     *
     * @return null or first ancestor that is not an Expression.
     */
    public ExpressionNode getExpressionOwner() {
        ExpressionNode parent = exprGetParent();
        while ((null != parent) && (parent instanceof Expression))
            parent = parent.exprGetParent();
        return parent;
    }

    //=============== ExpressionNode methods ================

    /**
     * This pair of methods are used to inform the node of its
     * parent.
     */
    public void exprSetParent(ExpressionNode n) {
        assertion(n != this, "Can not parent an expression to itself!");
        m_parent = n;
    }

    public ExpressionNode exprGetParent() {
        return m_parent;
    }

    /**
     * This method tells the node to add its argument to the node's
     * list of children.
     */
    public void exprAddChild(ExpressionNode n, int i) {
        assertion(false, "exprAddChild method not implemented!");
    }

    /**
     * This method returns a child node.  The children are numbered
     * from zero, left to right.
     */
    public ExpressionNode exprGetChild(int i) {
        return null;
    }

    /**
     * Return the number of children the node has.
     */
    public int exprGetNumChildren() {
        return 0;
    }

    //=============== SourceLocator methods ================

    /**
     * Return the public identifier for the current document event.
     *
     * <p>The return value is the public identifier of the document
     * entity or of the external parsed entity in which the markup that
     * triggered the event appears.</p>
     *
     * @return A string containing the public identifier, or
     * null if none is available.
     * @see #getSystemId
     */
    public String getPublicId() {
        if (null == m_parent)
            return null;
        return m_parent.getPublicId();
    }

    /**
     * Return the system identifier for the current document event.
     *
     * <p>The return value is the system identifier of the document
     * entity or of the external parsed entity in which the markup that
     * triggered the event appears.</p>
     *
     * <p>If the system identifier is a URL, the parser must resolve it
     * fully before passing it to the application.</p>
     *
     * @return A string containing the system identifier, or null
     * if none is available.
     * @see #getPublicId
     */
    public String getSystemId() {
        if (null == m_parent)
            return null;
        return m_parent.getSystemId();
    }

    /**
     * Return the line number where the current document event ends.
     *
     * <p><strong>Warning:</strong> The return value from the method
     * is intended only as an approximation for the sake of error
     * reporting; it is not intended to provide sufficient information
     * to edit the character content of the original XML document.</p>
     *
     * <p>The return value is an approximation of the line number
     * in the document entity or external parsed entity where the
     * markup that triggered the event appears.</p>
     *
     * @return The line number, or -1 if none is available.
     * @see #getColumnNumber
     */
    public int getLineNumber() {
        if (null == m_parent)
            return 0;
        return m_parent.getLineNumber();
    }

    /**
     * Return the character position where the current document event ends.
     *
     * <p><strong>Warning:</strong> The return value from the method
     * is intended only as an approximation for the sake of error
     * reporting; it is not intended to provide sufficient information
     * to edit the character content of the original XML document.</p>
     *
     * <p>The return value is an approximation of the column number
     * in the document entity or external parsed entity where the
     * markup that triggered the event appears.</p>
     *
     * @return The column number, or -1 if none is available.
     * @see #getLineNumber
     */
    public int getColumnNumber() {
        if (null == m_parent)
            return 0;
        return m_parent.getColumnNumber();
    }
}
